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# init(chassisBody:wheels:)

Creates a vehicle behavior.

```
convenience init(chassisBody: SCNPhysicsBody, wheels: [SCNPhysicsVehicleWheel])
```

## Parameters

`chassisBody`

A physics body to serve as the vehicle’s chassis.

`wheels`

An array of [`SCNPhysicsVehicleWheel`](/documentation/SceneKit/SCNPhysicsVehicleWheel) objects representing the vehicle’s wheels. A vehicle must have at least one wheel.

## Return Value

A new vehicle behavior.

## Discussion

Each object in the `wheels` array associates a node with the wheel to serve as its visual representation and defines properties for the wheel’s physical characteristics. Each wheel object must reference a unique node, which should be a child of the node containing the physics body used for the vehicle’s chassis. Typically, you load a node hierarchy representing the vehicle and all of its wheels from a scene file and then designate which nodes serve as the body and wheels.

For a behavior to take effect, you must add it to the physics simulation by calling the [`addBehavior(_:)`](/documentation/SceneKit/SCNPhysicsWorld/addBehavior(_:)) method on your scene’s [`SCNPhysicsWorld`](/documentation/SceneKit/SCNPhysicsWorld) object.

---

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